I'm not sure if this is possible(I've never seen a mod on economic buildings or agents), but as of right now when you play as the Punjab faction, there are no buildings or agents to spread Sikhism. If it is, here are some articles on possible buildings and units.
Building
Gurudwara
http://en.wikipedia.org/wiki/Gurudwara
AgentAmritdhara
http://en.wikipedia.org/wiki/Khalsa